The present invention generally relates to an implantable cardiac stimulation system and more particularly to a two lead universal cardiac stimulation system capable of sensing and applying pacing and defibrillating pulses to all four chambers of the heart. The present invention is further directed to such a system which includes a lead implantable in the coronary sinus region of the heart.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are usually positioned within the right side of the heart, either within the right ventricle or right atrium, or both, for making electrical contact with their respective heart chamber. Conductors within the leads and a proximal connector carried by the leads couple the electrodes to the device to enable the device to sense cardiac electrical activity and deliver the desired therapy.
Traditionally, therapy delivery had been limited to the venous, or right side of the heart. The reason for this is that implanted electrodes can cause blood clot formation in some patients. If a blood clot were released arterially from the left heart, as for example the left ventricle, it could pass directly to the brain potentially resulting in a paralyzing or fatal stroke. However, a blood clot released from the right heart, as from the right ventricle, would pass into the lungs where the filtering action of the lungs would prevent a fatal or debilitating embolism in the brain.
Recently, new lead structures and methods have been proposed and even practiced for delivering cardiac rhythm management therapy to the left heart. These lead structures and methods avoid direct electrode placement within the left atrium and left ventricle of the heart by lead implantation within the coronary sinus region of the heart. As used herein, the phrase xe2x80x9ccoronary sinus regionxe2x80x9d refers to the venous vasculature of the left ventricle, including any portions of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus.
It has been demonstrated that electrodes placed in the coronary sinus region of the heart may be used for left atrial pacing, left ventricular pacing, or cardioversion and defibrillation. These advancements enable implantable cardiac stimulation devices to address the needs of a patient population with left ventricular dysfunction and/or congestive heart failure which would benefit from left heart side pacing, either alone or in conjunction with right heart side pacing (bi-chamber pacing), and/or defibrillation.
Universal pacing and/or defibrillation systems capable of pacing and/or defibrillating all of the chambers of the right and left heart would of course require numerous pacing and/or defibrillation electrodes to be employed within the heart and its coronary venous system. Providing the numerous electrodes to implement such universal heart stimulation systems would in turn require an inordinate number of leads if currently available right and left heart leads were employed. This would result in unduly long implant procedures and possibly more leads than the human anatomy is able to accommodate. The number of leads required may also make it difficult to accurately locate each electrode at its most efficacious position within the heart.
Hence, there is a need in the art for new and improved right and left heart leads and lead configurations which provide efficient left heart access and integrated right and left heart therapies. Electrode placement on the leads should enable effective therapy and electrode selection to accommodate differences in heart physiology from one patient to another. Universal pacing and defibrillation systems that would result from the new and improved leads and lead configurations could provide significant improved therapies. Coordinated right heart and left heart pacing therapies would be made possible. Further, improved defibrillation therapies would also be made possible. The therapies could provide improved electrode configuration selection for improved defibrillation energy distribution within the heart or support improved sequential defibrillation pulse techniques. The present invention is directed to left heart leads and right and left heart lead configurations which address the above mentioned needs.
The invention provides an implantable cardiac stimulation system capable of sensing electrical activity of the heart in all four chambers of the heart and delivering pacing and defibrillation pulses to all four chambers of the heart. The system includes a lead system consisting of first and second leads. The first lead includes a right ventricular pacing electrode for placement in the right ventricle, a right ventricular defibrillation electrode for placement in the right ventricle, and a right atrial defibrillation lead for placement in the right atrium and/or the superior vena cava of the heart. The second lead includes a left ventricular pacing electrode for placement in electrical contact with the left ventricle, a left ventricular defibrillation electrode for placement in electrical contact with the left ventricle, a left atrial pacing electrode for placement in electrical contact with the left atrium, and a left atrial defibrillation electrode for placement in electrical contact with the left atrium of the heart, and a right atrial pacing electrode carried by one of the first and second leads for placement in the right atrium. The system further includes a cardiac stimulation device including a pulse generator that delivers defibrillation pulses between any combination of the defibrillation electrodes and pacing pulses to any one of the pacing electrodes and a sensing circuit that senses electrical activity of the heart with any one of the pacing electrodes.
In accordance with further aspects of the invention, the right ventricular defibrillation electrode, the right atrial defibrillation electrode, the left ventricular defibrillation electrode and the left atrial defibrillation electrode may be coil electrodes. Still further, the cardiac stimulation device may include a conductive case which may serve as a return electrode wherein the pulse generator of the cardiac stimulation device delivers defibrillation pulses between any combination of the defibrillation electrodes and the conductive case or pacing pulses between any one of the pacing electrodes and the conductive case.
The second lead is preferably implantable within the coronary sinus of the heart with the left ventricular pacing electrode, the left ventricular defibrillation electrode, the left atrial pacing electrode, and the left atrial defibrillation electrode spaced apart on the second lead so that when the left ventricular pacing electrode and the left ventricular defibrillation electrode are adjacent to the left ventricle within the coronary sinus of the heart, the left atrial pacing electrode and the left atrial defibrillation electrode are adjacent to the left atrium within the coronary sinus of the heart.